This invention relates to an ignition distributor arrangement for internal-combustion engines wherein the ignition distributor is fastened to the internal-combustion engine and is driven by a camshaft. The ignition distributor is aligned in the same direction as the axis of the camshaft and has a rotor which is substantially cylindrical in shape and which interacts with a cylindrical cam arranged at an end of the camshaft.
In a known arrangement of the above mentioned type (Porsche 944 Customer Service Information WKW 450 610, 07/81, Page 6), the rotor of the ignition distributor is arranged above the cam and is secured by a screw extending in a radial direction, i.e., transversely to the central longitudinal axis of the camshaft. A disadvantage of this arrangement is that the vibrations of the internal-combustion engine may cause loosening of the screw.
An object of this invention is to provide an improved ignition distributor arrangement wherein the fastening arrangement for the cam and the rotor securely withstands the vibrations occurring during the operation of the internal-combustion engine.
These and other objects are achieved in an ignition distributor arrangement for internal-combustion engines which comprises a generally cylindrical distributor rotor having a central longitudinal axis of rotation, and means for drivingly attaching the rotor to an end of the engine camshaft such that the central longitudinal axis of the rotor is aligned with a central longitudinal axis of the camshaft. In a preferred embodiment, a generally cylindrical cam is attached to the end of the camshaft by a screw. The cam has a flange which extends transversely to the central longitudinal axis of the camshaft. The rotor is fastened to the flange by means of an extension of the rotor, which is aligned with the flange, and one or more screws. The screws which attach the rotor to the cam are aligned such that their central longitudinal axis extends parallel to the central longitudinal axis of the camshaft. In an especially preferred embodiment, three spaced apart screws are used for fastening the rotor to the flange. In this embodiment, the rotor has an asymmetrical control finger. This control finger, the rotor extension, and the screws are arranged around the central longitudinal axis of the rotor so as to provide an essentially symmetrical distribution of mass around this axis, thus reducing vibrations when the engine is operating.
The outer diameter of the flange of the cam fits into an opening in a housing which surrounds a portion of the ignition distributor arrangement. The diameter of the opening is only slightly larger than the outside diameter of the flange.
The main advantages of the arrangement according to this invention are that a cam and rotor connection that is designed in this way is not loosened by vibrations occurring during operation of the internal-combustion engine. This result is due, at least in part, to the symmetrical distribution of mass at the rotor which avoids the occurrence of an unbalanced rotating mass.
Because the outside diameter of the flange is relatively close to the diameter of the opening, the rotor space is effectively closed with respect to the toothed-belt wheel space, making an additional dust cap unnecessary.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of a preferred embodiment of the invention, when considered in conjunction with the accompanying drawings.